Transformer unit



March 5, 1929.

C. E. STRYKER TRANSFORMER UNIT Filed April ll, 1927 'llll ,fd-J2 l 74A/ML, UM

Patented Mar. 5, 1929.

UNITED STATES PATENT OFFICE.

CLINTON E. STRYKER, OF `HIGHLAND PARK, ILLINOIS. ASSIGNOR T FANSTEEL PROD- .UCTS COMPANY, INC., OF NORTH CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

TRANSFORMER Unir.

My invention relates to a transformer unit and pertains especially to the type of a unit used to charge storage batteries, supply power for radio equipment, for operating railway signal relays, etc.

The object of my invention is to provide a unit in which the voltage applied to the rectifier may be carefully regulatedvto compensate for different battery loads, different internal characteristics of the rectifier cell,

and other operating conditions.

A further object of my invention is to provide an improved transformer with a secondary provided with a series of increments,

l5 whereby the secondary voltage range may be Varied in small steps throughout a wide range by the use of a small number of terminal posts.

Other objects will .be apparent as the de-y tailed description of my invention proceeds. In the accompanying drawing' wherein similar reference characters refer to like parts throughout:

Fig. 1 shows diagrammatically the improved unit, and

Fig. 2 shows the same unit connected to give a different secondary voltage. The most practical and permanent electrolytic rectifier now on the market is the type in which tantalum and lead electrodes areimmersed in an electrolyte of dilute sulphuric acid to which has been' added a-small amount of a salt of a metal of the iron group. These rectiiiers are well known and need no further description. However, forl optimum results it has been found that these rectitiers should be operated within a.cer tain deiinite voltage range. The life of the tantalum electrode depends, to a certain extent, on the nature of the film formed and this in turnis a function ofthe voltage applied to it; also different charging rates may berequired, and the charging rate of a storage battery naturally'v falls ol as the charging' process nears completion. y y Various methods have been devised for V regulatin the secondary voltage to compensate for t ese conditions, and it is common v practiceto use a variable resistance in series lwith the circuit to accomplish this result.

I have gfdes igned a transformer with a number of taps so arranged that it is possible to secure a secondary Ivoltage range of from 1/1 to 25% volts in 1/4volt steps. This 'arrangement permits an adjustment of chargingrate without the use ot' a resistance unit with resulting economies of operation. Also this transformer may be used to charge from 1 to 7 cells of batteries with one rectier cell.

In Fig. 1- the rectifier is represented by a receptacle 10 of suitable acid proof material, preferably glass, which contains an electrolyte 11 in which are immersed a tantalum electrode 12 and a lead electrode 13. The lead electrode is connected to the negative terminal of storage battery 14.

The transformer 15 includes a primary winding 16, preferably for use in a 115 volt circuit. This primary winding is tapped at 17 so that the primary may also be used at 100 volts. The secondary is divided into three windings, 18, 19 and 20, all of which are wound around the same core. The first secondary winding 18 is tapped to provide three increments and leads are taken from these increments to terminals A, B, C, and D. These increments are so proportioned that the potential difference between A and B is .25 volts; between B and C is .7 5 volts; and between C and D is .5 volts.

The second secondary winding 19 is divided into increments, the leads of which are connected to terminals E, F, G, and I-I, the voltage drop across the increments being 1.5, 4.5 and 3.0, respectively. The third secondary winding is tapped to provide two increments with leads to termin-als I, J and K, the voltage drop across the increments being 5 and 10, respectively.

The operation of my unit may be described as follows: Suppose that a givenrectiier cell charges a 6 volt storage battery at 1/2 ampere when the secondary voltage is 17.25 volts. A conductor 21 from the tantalum electrode is connected to terminal K. Terminal I is connected to terminal F by conductor 22. Terminal E is connected to terminal C by conductor 23, and terminal A is connected to the positive bolt of the storage battery by conductor 24.

By adding the-increments shown in Fig.v

1, it may be readily seen that the secondary voltage will be 17.25. If a 12 volt battery is to be charged'and a voltage of 22%C is required, connections may be made as shown in Fig. 2.' It will be apparent that should the charging rate decrease for any reason,

it may be adjusted by stepping up the voltage the required amount.

While I have described in detail a pre;

steps by the use ofa small number of terminal posts.

20 2. A transformer whose secondary is provided with taps dividing it into successive increments in the ratio of 1:3:2 wherebyequal voltage increments may be obtained from different combinations.

3. In a transformer, a primary winding, a plurality of secondary windings, the secondary windings being divided into successive increments in the ration of 1:3:2, the

smallest increment of one winding corresponding to the sum of the increments of another winding and means whereby the .increments may be selectively connected to other increments or series of increments 1 whereby the secondary voltage may be varied in small equal steps throughout a wide range by the use of a small number of terminal posts.

In witness whereof, I hereunto subscribe my name this 6th day of April, 1927.

CLINTON E. STRYKER. 

